Savory snack food items, such as potato chips, corn chips and popcorn, are highly sensitive to oxygen and moisture and tend to rapidly become stale if exposed to room air for even a relatively short period of time. Savory snack food items are usually packaged in bags manufactured from a flexible film material having inherent moisture- and oxygen-barrier properties. Examples of suitable materials include waxed paper, metal foil, thermoplastic film and the like. Frequently, snack food packages are constructed from a laminate film consisting of a plurality of layers. While the respective layers may have a variety of properties, at least one layer is selected so as to provide each of the needed moisture and oxygen barrier properties.
The flexible film materials frequently used in constructing snack food packages are resistant to folding, and have a property often referred to as "memory." Thus, simply folding or rolling the open upper end of the package does not function to create an airtight (and moisture-tight) seal. As is well known by the consumer, the folded bag tends to unfold to some degree, leaving its upper end open and the product exposed to moisture in the ambient air. In this state the product becomes stale in a relatively short period of time.
A variety of devices have been produced to facilitate re-closing these flexible snack food packages. Devices such as clothes pins, clamps, clips, etc. frequently are used by consumers to re-close such packages in an airtight manner. Another solution to this problem has been to provide closure devices which are integral with the snack food package itself. One example of this latter concept is seen in U.S. Pat. No. 4,584,201 (Jan. 20, 1976; Boston) which discloses a resealable package and method of making the same. This patent teaches the application of an adhesive "seal strip" to the external surface of the bag. The seal strip is protected prior to use by a removable release strip. Once the bag is opened, the release strip is removed to expose the adhesive, and the bag is folded down a number times so that the external surface of the bag contacts the adhesive strip and thus cannot unfold.
U.S. Pat. No. 4,428,477 (Jan. 31, 1984; Christofolo) discloses a resealable package for premoistened towelettes. The package is in the shape of an inverted "T", and is re-sealed by folding over the base of the "T" and securing it to an adhesive strip disposed along an outer edge of the package.
Canadian Patent No. 886,404 issued on Nov. 23, 1971 discloses a re-closeable bag having a bendable wire secured longitudinally along the back seam of the bag. The wire is located close enough to the top of the bag so that it is folded along with the upper portion of the bag. The resilient nature of the wire prevents the bag from unfolding.
As far as is known, none of the re-sealable packages having integral closure devices as mentioned above has been widely accepted by either the snack food industry or the consumer. The cost associated with manufacturing such resealable packages has tended to discourage their wide use. The added complexity during film production and during packaging slows production, also leading to increased cost. Thus, there remains a need in the art for a convenient, re-closeable snack food bag that is inexpensive to manufacture, effective and widely accepted by consumers.